linux-kernel - [PATCH 3.16 249/305] hfs: do not free node before using

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Message-ID: <lsq.1549201508.994027445@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Ernesto A. Fernandez" <ernesto.mnd.fernandez@...il.com>,
        "Pan Bian" <bianpan2016@....com>, "Joe Perches" <joe@...ches.com>,
        "Viacheslav Dubeyko" <slava@...eyko.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>
Subject: [PATCH 3.16 249/305] hfs: do not free node before using

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Pan Bian <bianpan2016@....com>

commit ce96a407adef126870b3f4a1b73529dd8aa80f49 upstream.

hfs_bmap_free() frees the node via hfs_bnode_put(node).  However, it
then reads node->this when dumping error message on an error path, which
may result in a use-after-free bug.  This patch frees the node only when
it is never again used.

Link: http://lkml.kernel.org/r/1542963889-128825-1-git-send-email-bianpan2016@163.com
Fixes: a1185ffa2fc ("HFS rewrite")
Signed-off-by: Pan Bian <bianpan2016@....com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Joe Perches <joe@...ches.com>
Cc: Ernesto A. Fernandez <ernesto.mnd.fernandez@...il.com>
Cc: Viacheslav Dubeyko <slava@...eyko.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/hfs/btree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/hfs/btree.c
+++ b/fs/hfs/btree.c
@@ -328,13 +328,14 @@ void hfs_bmap_free(struct hfs_bnode *nod
 
 		nidx -= len * 8;
 		i = node->next;
-		hfs_bnode_put(node);
 		if (!i) {
 			/* panic */;
 			pr_crit("unable to free bnode %u. bmap not found!\n",
 				node->this);
+			hfs_bnode_put(node);
 			return;
 		}
+		hfs_bnode_put(node);
 		node = hfs_bnode_find(tree, i);
 		if (IS_ERR(node))
 			return;